Battery packs wherein 100 or more storage cells are connected in series are used commonly in electric vehicles or hybrid vehicles. However, repetitive charging/discharging cycling of the battery packs will lead to increasing disparities between the remaining capacities of the individual storage cells that structure the battery packs, resulting in non-uniformity of the remaining capacities. The result is a reduction in the effective capacity of the battery pack, which reduces the life expectancy of the battery pack. Because of this, there is the need for a technology to equalize the remaining capacities of storage cells that structure a battery pack.
One example of a technology for equalizing the remaining capacities of storage cells that structure a battery pack is described in Patent Reference 1, below. In this technology described in Patent Reference 1, one end of an inductances connected to a contact point between two storage cells B1 and B2 that are connected in series, and the voltages of the two storage cells are equalized through executing, at appropriate times, an operation for repetitively switching, at short time intervals, between a first mode wherein an electric current flows in a first closed circuit that is formed by connecting the other end of the inductance to the other end of the storage cell B1, and a second mode wherein an electric current flows in a second closed circuit that is formed by connecting the other end of the inductance to the other end of the storage cell B2.
Japanese Unexamined Patent Application Publication 2001-185229 discloses a need for the provision of one inductance for each two storage cells. Because of this there would be the need to provide a total of 50 inductances for a battery pack wherein 100 storage cells are connected in series. The result is that when the number of storage cells increases, the number of inductances increases as well, and thus the device dimensions and device costs increase as well.
Additionally, in the technology disclosed in Japanese Unexamined Patent Application Publication 2001-185229, for each two storage cells it is necessary to provide a pair of switching elements for repetitively alternating between the first and second modes. These switching elements perform switching at a high switching frequency, and thus produce electric radiation noise and transmission noise. Because of this, when the number of batteries is increased, the number of switching elements also increases, increasing the noise as well.
Given this, the object of the present invention is to provide a remaining capacity equalizing device and method, and a remaining capacity equalizing device set, capable of achieving the equalization of the remaining capacities of a plurality of storage cells that are connected in series to structure a battery pack, using a small number of inductances and switching elements.